Method for the purification of copper chloride solution

ABSTRACT

The invention relates to a method for the removal of metal impurities in chloride-based copper recovery processes. The amount of impurities in a strong chloride solution of monovalent copper can be reduced according to the method down to very low levels by using ion exchange as at least one purification stage.

The invention relates to a method for the removal of metal impurities ina chloride-based copper recovery process. According to this method, theamount of metal impurities in a strong chloride solution of monovalentcopper can be reduced to very low levels by using ion exchange as atleast one purification stage, especially chelating ion-exchange resins.

U.S. Pat. No. 6,007,600 describes a method for the hydrometallurgicalproduction of copper from copper-containing raw materials such as coppersulphide concentrate. According to the method the raw material isleached counter-currently with a strong sodium chloride-copper chloridesolution in several stages to form a monovalent copper(I) chloridesolution. Since both some divalent copper chloride and impuritiescomposed of other metals always remain in the solution, reduction of thedivalent copper and solution purification are performed. The purecuprous chloride solution is precipitated with sodium hydroxide tocopper oxidule (cuprous oxide) and the oxidule is reduced further toelemental copper. The sodium chloride solution generated during copperoxidule precipitation is treated further in chlorine-alkalielectrolysis, and the chlorine gas and/or chloride solution obtainedfrom this is used in raw material leaching, the sodium hydroxide formedin electrolysis for oxidule precipitation and the forming hydrogen forthe reduction of copper to elemental copper. U.S. Pat. No. 6,007,600focuses on the copper recovery method as a whole, but solutionpurification for example is not described in detail.

U.S. Pat. No. 5,487,819 also describes a method for thehydrometallurgical production of copper from a copper-containing rawmaterial such as copper sulphide concentrate. According to the method,the raw material is leached counter-currently with a sodiumchloride-copper chloride solution in several stages in order to form amonovalent copper(I) chloride solution. The solution generated issubjected to ordinary solution purification as hydroxide precipitation,described in example 6. Zinc and lead contents in the cuprous chloridesolution after solution purification are at a level of 2-3 g/l, and thesolution is fed to copper electrolysis.

When one wishes to reduce the impurity level of a copper chloridesolution as much as possible, for instance down to a few mg/l or less,ordinary hydroxide precipitation is not sufficient to reach this level,without a great deal of copper being precipitated together withimpurities. It is of course clear that it is worth precipitating themajority of metal impurities by normal methods, but the finalpurification has been problematic, since for instance the permittedimpurity content of LME-A level cathode copper is rather small (BS6017:1981).

In the types of processes described above the original material i.e.copper concentrate is leached into a strong alkali chloride solution,containing for example at least 200 g/l NaCl or other alkali chloride.Copper and metal impurities are then present in the solution as chloridecomplexes, usually with a negative charge. Copper is mainly present inthe solution in mono-valent form.

In their article: “Ultra high purification of copper chloride solutionsby anion exchange”, Hydrometallurgy 45 (1997), pp. 345-361, Kekesi, T.and Isshiki, M. suggested anion-exchange resins for the purification ofa copper chloride solution. The disadvantage is however, that itrequires a large quantity of resin, multi-stage washing to remove metalimpurities from the resin, and a separate stage for the separation oflead for example.

Chelating ion exchangers have been researched for the removal of basemetals such as zinc, cadmium, copper and nickel from metal platingsolutions. One study is described in the article by Koivula, R. et al:“Purification of metal plating rinse waters with chelating ionexchangers”, Hydrometallurgy 56 (2000) pp. 93-108. The chloride contentsof the solutions were however in the range of some milligrams per litre.

U.S. Pat. No. 4,895,905 describes a method for the removal of alkaliearth or heavy metals from a strong NaCl solution using chelatingresins. The amount of alkali earth and heavy metals before resintreatment was at the most about one hundred mg/l and after treatment themajority of metals were undetectable. The patent concentrates largely onresins where the functional group is alkylaminophosphonic.

The method of the invention relates to the removal of metal impuritiesfrom a strong chloride solution of monovalent copper to the level wherethe amount of metal impurities is only a few milligrams per litre. Theremoval of metal impurities is implemented at least partly using ionexchange, in particular with chelating ion-exchange resins. The termstrong chloride solution refers to a solution where the amount of alkalichloride such as sodium chloride is at least 200 g/l. The amount ofcopper, especially monovalent copper, in the solution is in the order of30-100 g/l. Particularly in processes where the final product, metalliccopper, is formed by precipitation, the amount of metal impuritiesshould be reduced in the solution from which the precipitation is tooccur, since the impurities will be precipitated alongside the copper inthe precipitation stage.

The essential features of the invention will be made apparent in theattached claims.

If divalent copper is present in the monovalent copper chloridesolution, it is first removed by some appropriate method. The principalmetal impurities in copper concentrate are zinc, lead, nickel, iron andmanganese, and they appear in a chloride solution in divalent ortrivalent form. The majority of unwanted divalent metals can mostadvantageously be removed using conventional precipitation methods suchas hydroxide precipitation.

Precipitation can however be carried out in connection with the methodaccording to the present invention so that 0.1-1 g/l of metal impuritiesare left in the solution. This avoids the precipitation of copper alongwith other metals, which would cause fruitless recirculation and copperlosses.

The removal of metal impurities from a copper chloride solution down toa level of a few milligrams is performed using a chelating ion-exchangeresin. The functional group of ion-exchange resin is preferably theiminodiacetic acid group or the aminophosphonic group(—CH₂—NH—CH₂—PO₃Na₂). The property they have in common is astyrene-divinyl-benzene matrix of ring structure and a certainfunctional group that is selective for certain metals. A divalent ortrivalent metal, such as zinc, lead, nickel, iron and manganese, can bebound to the functional group in place of the sodium. Since the resindoes not bind monovalent copper so strongly, it remains in the chloridesolution and passes through the resin. The metals bound to the resin areeluted with hydrochloric acid and the solution obtained is returned tothe process so that the metal impurities are finally removed from theprocess via the precipitation stage.

Since the resin used binds divalent copper about as strongly as it bindsthe metal impurities, the oxidizing effect of the air must be eliminatedso that the monovalent copper is not oxidized into divalent.

The dissolution of monovalent copper into water is based on chloridecomplexes so that the solution is stable only in a strong chloridesolution, an acidic or neutral environment. Therefore the processsolution that is the mother liquor in the resin (monovalent copperchloride solution) has to be displaced with an NaCl solution beforeelution, and correspondingly before the process solution is fed into theresin after regeneration, the equipment that contains resin must befilled with an NaCl solution instead of the alkaline regenerationsolution.

We have found that by using the above ion-exchange resin for thepurification of monovalent copper chloride solution it is possible toachieve an impurity level in the solution that corresponds to cathodecopper grade LME-A or even purer.

The method is described further by the following examples.

EXAMPLE 1

Tests were carried out in 50 ml burettes. The feed rate of the solutionthrough the column was 300 ml/h. Samples of the outflowing solution weretaken every hour. After the test 150 ml of NaCl solution was fed throughthe column, after which the column was eluted with a 10% HCl solutionfor three hours at a rate of 100 ml/h. During elution 5 samples weretaken. After elution 150 ml of water was fed through the column andfinally the resin was regenerated by feeding 300 ml of NaOH solution(NaOH=80 g/l) through the column.

The solution for purification contained about 200 mg/l of lead and zinc,and about 50 mg/l of iron, manganese and nickel, and its pH was 6. Thesame solution was fed to each of the three columns with separate hosepumps.

Three resins were used in the tests in parallel columns. A summary oftheir basic characteristics is shown in Table 1. TABLE 1 Properties ofion-exchange resins used in tests Resin I II III Matrix Styrene StyreneStyrene divinylbenzene divinylbenzene divinylbenzene Func- Iminodiacetic—CH₂—NH—CH₂—PO₃Na₂ Iminodiacetic tional group Ion Na⁺ Na⁺ Na⁺ formCapac- ≧1.25 ≧1.0 ≧1.0 ity, eq/l

TABLE 2 Ion-exchange test results TIME Cu Zn Pb Fe Mn Ni TEST SAMPLEh/min g/L mg/L mg/L mg/L mg/L mg/L Resin I Charging Feed solution 52.8203 140 49.0 37.8 36.6 Charging 1 h 52.0 <0.5 <1 2.9 <0.25 <0.5 Charging2 h 53.9 <0.5 <1 3.1 0.51 <0.5 Charging 3 h 53.5 0.66 23.0 4.7 3.5 <0.5Brine rinse Composite sample 11.0 63.9 146 1.6 16.2 1.7 Elution 15 min0.447 907 124 416 1012 943 Elution 30 min 0.516 3 355 1 466 209 132 227Elution 1 h 0.124 1 195 1 010 0.86 0.38 2.2 Elution 2 h 0.035 352 690.34 <0.1 0.35 Elution 3 h 0.010 166 2.4 0.39 <0.1 0.37 Water rinseComposite sample 0.003 144 <1 0.45 <0.1 <0.2 Regeneration Compositesample 0.001 1.4 <1 0.30 <0.1 <0.2 Resin II Charging Feed sample 52.8203 140 49.0 37.8 36.6 Charging 1 h 52.6 <0.5 <1 1.4 <0.25 <0.5 Charging2 h 51.5 <0.5 <1 7.6 <0.25 <0.5 Charging 3 h 53.3 <0.5 5.2 4.0 0.45 <0.5Brine rinse Composite sample 11.4 36.7 70.6 1.1 5.1 3.8 Elution 15 min1.06 4 130 570 11.4 2 120 3 610 Elution 30 min 0.242 2 850 1 490 102 1184.1 Elution 1 h 0.064 465 1 500 17.8 <0.1 <0.2 Elution 2 h 0.009 68.5950 6.9 <0.1 <0.2 Elution 3 h 0.002 11.1 1.6 1.2 <0.1 <0.2 Water rinseComposite sample 0.024 7.4 <1 0.44 <0.1 0.28 Regeneration Compositesample 0.002 2.5 <1 3.0 <0.1 <0.2 Resin III Charging Feed sample 52.8203 140 49.0 37.8 36.6 Charging 1 h 35.3 <0.5 <1 1.2 0.25 <0.5 Charging2 h 53.0 <0.5 5.5 3.7 1.1 <0.5 Charging 3 h 54.7 <0.5 35.7 2.9 6.7 <0.5Brine rinse Composite sample 13.1 31.0 45.8 1.6 7.7 0.7 Elution 15 min0.813 410 73.3 383 778 764 Elution 30 min 0.931 2 395 1 620 133 135 165Elution 1 h 0.457 986 975 1.0 0.33 1.1 Elution 2 h 0.190 379 111 0.51<0.1 <0.2 Elution 3 h 0.076 190 9.5 0.77 <0.1 <0.2 Water rinse Compositesample 0.019 360 3.4 0.25 <0.1 <0.2 Regeneration Composite sample 0.0104.7 <1 0.40 <0.1 <0.2

Table 2 shows that all the selected resins were able to remove theimpurities required. Resin II performed best, being able to produce asolution of the required purity in over two hours. The selected resinsacted far better in a copper(I) chloride-sodium chloride solution thanother resins that were tried, which were unable to perform selectivelyas desired.

EXAMPLE 2

A pilot test was carried out in glass columns with an outer diameter of70 mm (wall thickness 4.2 mm) and a height of 1000 mm (straightsection). The total volume of the column was 3 litres and 2 litres ofresins were then added. The resin used in the pilot was resin II. Therewere two columns in series in the run and the flow occurred from the topto the bottom without intermediate pumping. In front of the columnsthere was a column filled with copper chips, with the purpose ofreducing the copper that had oxidized during intermediate storage tomonovalent copper.

At first both columns were changed once every 24 hours and eluted. Lateronly the first of the columns was subjected to elution, the secondcolumn was used as the first and the ready eluted column was used as thefinal column. The elution frequency was changed so that it depended onthe amount of impurities in the feed solution, generally every 2-3 days.

In the first test campaign the concentrate used contained very littlenickel and manganese and thus their amount in the ion-exchange feedsolution was below the analysis limit. The zinc content in the feedsolution varied between 100-900 mg/l with an average of 340 mg/l. Thelead content varied between 3-70 mg/l with an average of 21 mg/l. In theproduct solution 80% of the zinc analyses were below the analysis limit(0.5 mg/l) as were 58% of the lead analyses (analysis limit 1 mg/l). Inthe analyses of the copper product reduced from copper oxidule zinc wastypically below 1 ppm and lead below 0.5 ppm.

In the second test campaign a concentrate was used with a lead contentof about twice that of the concentrate used in the first campaign. Thecontents of the impurities relevant with regard to ion exchange did notdiffer greatly from those of the previous campaign.

The zinc content of the feed solution varied in this campaign between120-920 mg/l with an average of 390 mg/l. The lead content at the startof the series was 75 mg/l, rising to a level of 440 mg/l at the end ofthe series. Nickel was again below the analysis limit of 0.5 mg/l, andthe manganese content was between 0.1-1.2 mg/l.

95% of the product solution zinc analyses were below the analysis limit(0.5 mg/l) as were 42% of the lead analyses (analysis limit 1 mg/l). Thenickel and manganese contents were again very low.

In the analyses of the copper product reduced from copper oxidule zincwas on average 1.3 ppm and lead 0.55 ppm i.e. the copper product was ofLME-A quality.

1. A method for the removal of metal impurities in chloride-based copperrecovery processes, comprising removing the metal impurities from astrong chloride solution of monovalent copper using chelatingion-exchange resins.
 2. A method according to claim 1, wherein there isa styrene-divinyl-benzene matrix of ring structure in the ion-exchangeresin.
 3. A method according to claims claim 1, wherein the functionalgroup of the ion-exchange resin is the iminodiacetic acid group.
 4. Amethod according to claim 1, wherein the functional group of theion-exchange resin is the aminophosphonic group.
 5. A method accordingto claim 1, wherein the metal impurity to be removed is selected fromthe group consisting of zinc, nickel, lead, iron and manganese.
 6. Amethod according to claim 1, wherein the alkali chloride content of thestrong chloride solution is at least 200 g/l.
 7. A method according toclaim 1, wherein the amount of monovalent copper in the solution to bepurified is 30-100 g/I.
 8. A method according to claim 1, wherein theremoval of metal impurities is carried out in an acidic environment. 9.A method according to claim 1, wherein the removal of metal impuritiesis carried out in a neutral environment.
 10. A method according to claim1, wherein the copper-containing chloride solution that is the motherliquor in the resin is displaced before elution with an NaCl solutionand that the alkaline solution to be used for regenerating the resin isdisplaced with an NaCl solution before the copper-containing chloridesolution is fed into the resin.
 11. A method according to claim 1,wherein the majority of the metal impurities in the strong chloridesolution of monovalent copper are removed by hydroxide precipitation andthe rest by using ion exchange.
 12. A method according to claim 11,wherein the metal impurities are removed by hydroxide precipitation to acontent of 0.1-1 gil, after which the final purification is made usingion exchange.
 13. A method according to claim 1, wherein impurities areremoved from a strong chloride solution of copper by ion exchange atleast to a level that corresponds to cathode copper LME-A grade impuritylevel.